CMMVC8273E Host cannot be removed as there is a volume that is accessible from multiple iogrps including one of the iogrps specified.
Explanation
If a volume is mapped to a host, it must be mapped
in all of the iogrps in which it is accessible. The rmhostiogrp command
fails if it would leave the system in this state.
User response
Use lshostvdiskmap to find the list of volumes that are mapped to the host in multiple iogrps. Then for each one either a) remove the host/volume mapping or b) remove the iorgp that the host is being removed from the volume's access iogrp set.